Wet type gas scrubber

ABSTRACT

A wet gas scrubber, wherein a mechanism for dividing a gas flow into two and for making the cross-sectional area of the gas flow paths variable is provided in a throat part and guides are provided respectively on the upstream side and downstream side of said mechanism so that the pressure loss may be reduced and further the relation between control variables of the variable cross-sectional area mechanism and the gas flow rate may be linearized. The guides are wedge-shaped with the broad ends at the variable mechanism. In one embodiment the variable mechanism comprises a rotor shaft extending transversely of the throat part and a rotor mounted on the shaft. The rotor has a rectangular longitudinal cross section and a transverse cross section which has a different length than width. The rotor has a transverse cross section bounded by a closed curve. In another embodiment the variable mechanism comprises a pair of spaced flexible and stretchable plate members extending along the inside portions of the throat parts. Plate moving elements are connected between the plate parts and are coupled to the plate members for bending the plate members outwardly into the throat parts. In still another embodiment the variable mechanism comprises two spaced sets of bulkhead plates extending along the inside portions of the throat parts. Each set including a first bulkhead plate having one end pivotally mounted on the venturi tube adjacent one gas flow guide and a second bulkhead plate slidably mounted adjacent the other gas flow guide and hingedly coupled to the first bulkhead plate. Plate moving members are connected between the sets of plates and are coupled to the sets of plates for moving the sets of bulkhead plates outwardly into the throat parts.

United States Patent [72] Inventor Akiyoshi Ueda Kitakyushu, Japan [21]Appl. No. 660,342

[22] Filed Aug. 14, 1967 [45] Patented Jan. 19,1971

{73] Assignee Nippon Steel Corporation Tokyo,,lapan [32] Priority Aug.15, 1966 [33] Japan [54] WET TYPE GAS SCRUBBER 6 Claims, 9 Drawing Figs.

52 user 261/62, 261/118. 138/46, l37/525,239/265.43

51 1m.c1 B0lf3/04, B01d47/10,B01d47/06 so FieldofSearch 261/115,

62, 52,44,118, V.S., VV, U.V., 11,12,13; 251/358. 334. 342. 60: 60/271;l38/44,45,46: 239/265.43', 137/525 [56] References Cited UNITED STATESPATENTS 1,045,613 11/1912 Roth 261/52 1,555,489 9/1925 Spencer et a1.261/44 2,059,687 11/1936 Gagg 251/358X 2,424,654 7/1947 Gamble 261/V.S.2,472,949 6/1949 Jacksonm. 138/45 2,797,904 7/1957 Voorheis 261/1 18X2,905,543 9/1959 Schreter et al.. 48/180X 3,134,223 5/1964 Ball,Jr.60/271X 3,284,064 1 1/1966 Kolm et a1. 261/62 3,350,076 10/1967Crommelin, Jr

ABSTRACT: A wet gas scrubber, wherein a mechanism for dividing a gasflow into two and for making the cross-sectional area of the gas flowpaths variable is provided in a throat part and guides are providedrespectively on the upstream side and downstream side of said mechanismso that the pressure loss may be reduced and further the relationbetween control variables of the variable cross-sectional area mechanismand the gas flow rate may be linearized. The guides are wedge-shapedwith the broad ends at the variable mechanism. In one embodiment thevariable mechanism comprises a rotor shaft extending transversely of thethroat part and a rotor mounted on the shaft. The rotor has arectangular longitudinal cross section and a transverse cross sectionwhich has a different length than width. The rotor has a transversecross section bounded by a closed curve. In another embodiment thevariable mechanism comprises a pair of spaced flexible and stretchableplate members extending along the inside portions of the throat parts.Plate moving elements are connected between the plate parts and arecoupled to the plate members for bending the plate members outwardlyinto the throat parts. In still another embodiment the variablemechanism comprises two spaced sets of bulkhead plates extending alongthe inside portions of the throat parts. Each set including a firstbulkhead plate having one end pivotally mounted on the venturi tubeadjacent one gas flow guide and a second bulkhead plate slidably mountedadjacent the other gas flow guide and hingedly coupled to the firstbulkhead plate. Plate moving members are connected between the sets ofplates and are coupled to the sets of plates for moving the sets ofbulkhead plates outwardly into the throat parts.

FIG.2

FIG.

INVENTOR Ak/yosh/ Ueda wa r PATENTEU m1 9 I97! 3553489 SHEET 2 OF 4INVETOR Akl'yoshi Ueda I Q Mat/441% 2m PATENTEDEJAN 1 9 m7:

SHEET 3 OF 4 IN VENTOR Ak/yoshi Ueda PATENTEDJANWQ?! 3556.489

SHEET 4 BF 4 INVENTOR Akiyosh/ Ueda BY v w y/M WET TYPE GAS SCRUBBERThis invention relates to improvements in venturi-type gas scrubber.

In venturi-type gas scrubber, there are already known various methodswhereby the cross-sectional area of the throat part can be varied inresponse to operating conditions. That is to say, a controllingequipment for varying cross-sectional area is provided in the throatpart of a scrubber so that the gas flow rate passing through the throatpart may be varied. In such method, unnecessary vortex and separation ofboundary layer will be produced in the gas flow after the throat part.and the recovery of the pressure loss to be obtained in the diffusingpart, that is, the portion to be regained by converting the dynamicpressure to a static pressure will be entirely lost. Further, as therelation between the gas flow rate and the control variable is not of alinear function, the controlling of gas flow rate by means of anactuator of the conventional controlling device can not cover the entireactuating span, but can be carried out only in a limited narrow rangeeach time, while dividing the entire span to several such narrow ranges.

Therefore, as compared with the present invention such conventionalmethod had various disadvantages such as an increase in gas pressureloss, power and size up of blowers or a reduction in gas pressure afterpassing through the scrubber, resulting in increases of variousequipment costs and operat ing costs. Further, even the gas flow ratehad to be controlled by partially linearizing the nonlinearcharacteristics of the actuator.

The present invention is a venturi-type gas scrubber wherein, forexample. a rotatable rotor or a variable-shape diaphragm formed of amaterial high in the elongation percentage and elasticity or avariable-shape bulkhead plate having a rotating joint and a slidingjoint to vary the cross-sectional area of the gas flow path is providedin a substantially intermediate part of the gas flow path in a throatpart so that the gas passing through the throat part may be divided intotwo paths and the gas flow rate may be variable and an introducing partis formed in the contracting part of the gas flow 1 path arranged on theupstream side of the throat part and a pressure recovering part isformed in the diffusing part of the gas flow path arranged on thedownstream side of the throat part. It is one of the features that, withthe introducing part and the pressure recovering part the gas flow pathis divided into two and the greater part of the variable cross-sectionalarea mechanism is enclosed so that the gas will not collide directlywith the variable cross-sectional area mechanism in the throat part andunnecessary vortexes and separation of boundary layer produced in thegas flow paths can be prevented. Further, when the shapes of the partsof the variable crosssectional area mechanism inserted in the throatpart to vary the cross-sectional area of the flow paths are made proper,the relation between the gas flow rate through the paths and the controlvariable (such as, for instance, in the case of the rotor a rotatingangle of the axis) of said mechanism may be made close to a linearfunction over a wide range, whereby the characteristics of the actuatingpart for the controlling equipment can be made excellent. Further,according to the present invention a high dust collecting efficiency canbe obtained even with the varying gas flow rate.

As described above, in the present invention a variable cross sectionalarea mechanism is inserted in the throat part of the gas scrubber sothat the cross-sectional area of the gas passage can be varied inresponse to the varying gas flow rate and further a gas introducing partand a pressure recovering part are formed as follows: That is, guideplates are provided respectively on the upstream side and downstreamside of the variable cross-sectional area mechanism so as to divide thegas path in two. By such formation, in the throat part a conversion froma static pressure of gas to a dynamic pressure and in the pressurerecovering part a conversion from the dynamic pressure to the staticpressure can effectively be performed, and the pressure loss of theentire equipment can be reduced. Further, by selecting properly the formof the curve made on the outer periphery of the variable bulkhead platepart in contact with the gas, the relationship between the gas flow rateand the control variable of the cross-sectional area mechanism can belinearized in a wide range. Therefore. it can be used effectively as anactuating part for the controlling device over a wide range of the inputamount (control variables) in said mechanism. 1

An object of the present invention is toprovide a wet gas scrubber inwhich the pressure loss is small and a high dust collecting efficiencycan be obtained.

Another object of the present invention is to provide a wet gas scrubberin which the cross-sectional area of the gas passage can be varied inresponse to the changes of the gas flow rate and which has excellentcharacteristics as an actuating part for the controlling device.

Other objects will become clear from the following explanation andaccompanying drawings.

FIG. 1 is a vertically sectioned view of an embodiment of the presentinvention in which a rotor is applied for the variable cross-sectionalarea mechanism in a venturi-type gas scrubber.

FIG. 2 is a sectioned view on line 1-1 in FIG. 1.

FIG. 3 is a sectional view of a variable cross-sectional area mechanismformed mostly of a material capable of high elongation and having highelasticity.

FIG. 4 is an enlarged view of a part of FIG. 3.

FIG. 5 is a sectional view of a variable cross-sectional area mechanismformed of variable-shape bulkhead plates having a rotating joint and asliding joint.

FIG. 6 is a schematic view of an embodiment of the present inventionwherein a rotor is used for the variable cross-sectional area mechanism.

FIG. 7 is a schematic view illustrating the case of removing the guideplates in the contracting part and the diffusing part occupying a partof the present invention shown in FIG. 6.

FIG. 8 is a graph in which the distance from the inlet of a venturiscrubber is taken on the abscissa and the static pres sure at each pointin the direction of the flow of the venturi scrubber is taken on theordinate.

FIG. 9 is a graph in which the abscissa is the same as in FIG. 8 and thevelocity at each point in the direction of the flow of the venturiscrubber is taken on the ordinate. In FIGS. 8 and 9, the static pressureand velocity at each point in the case of FIG. 6 are indicated withsolid lines and the static pressure and velocity at each point in thecase of FIG. 7 are indicated with dotted lines for comparison.

The details of the present invention shall be explained with referenceto the drawings.

FIGS. 1 and 2 show an equipment of the present invention in aventuri-type gas scrubber wherein a rotor is applied to the variablecross-sectional area mechanism. The inside of an outer wall 2 and theouter periphery of a wedge-shaped guide 1 form two-divided contractingparts A and P of the flow path as introducing parts into a scrubber forraw gas. The inside of an outer wall 5 and the outside of a rotor 3 formthroat parts B and Q. The inside of an outer wall 7 and the outside of awedge-shaped guide 6 form two-divided diffusing parts C and The raw gaswill gradually increase its velocity while passing through thecontracting parts A and P and will proceed to the throat parts B and Q.When the gas passes through the narrowest parts between the projectingend parts of the rotor 3 and the inside of the outer wall 5 in thethroat parts B and Q, the gas velocity will reach a maximum value.

An example of the rotor 3 to be used in this embodiment as shown in FIG.2 is a rectangular column which has such a right cross-sectional area asthe area enclosed by any closed curves and in which the ratio of thelength to the width of the cross section is different. Therefore, byrotating a rotor axis 4 intersecting at right angles with thelongitudinal axis of gas flow, the cross-sectional area of the throatpan can be made variable, the fluid resistance can be reduced andfurther the rela tion between the control variable and the gas flow ratecan be made a linear function. A solid having a closed and curvedsurface can also be used instead of the above mentioned rectangularcolumn.

Another embodiment of the variable cross-sectional area mechanism isshown in FIG. 3. A part of FIG. 3 as magnified is shown in FIG. 4. Thatis, a plurality ofliners 11 are attached to the gas side surface of aflexible plate 10 formed of a material which can be highly elongated andhaving a high elasticity so as to protect the flexible plate 10 so thata diaphragm of a variable shape can be formed by the variation of theclearance between the liners 11 in response to the elongation andcontraction of the flexible plate 10.

The torque from a driving axle 17 is transmitted to a rod 14 through apin 15 from a crank plate 16. As the rod 14 is fitted through a fittingseat plate 12 fixed to the flexible plate 10 and liners I1 and a pin 13,the positions of the flexible plate 10 and liners 11 are so determinedthat the torque acts to push out or pull back the flexible plate 10,liners 11 and fitting seat plate 12 as a whole, whereby a desiredcross-sectional area of the throat parts B and Q can be obtained.

Thus, the cross-sectional area of the throat part can be made variable.At the same time, a guide plate 1 is provided in the upstream part todivide the gas current in two so that the gas will not collide directlywith the variable cross-sectional area mechanism and a guide plate 6 isprovided in the downstream part to recover the velocity obtained in thethroat part again as a static pressure so that the pressure loss can bereduced.

The shape of each of the guide plates 1 and 6 is not specified but ispreferably wedge-shaped. Specifically, it is preferable that the guideplate 6 should have a length of about to 7 times as large as the widthof the throat part B. Further, its apex angle a may be 6 to 13.

A third embodiment of the variable cross-sectional area mechanism isshown in FIG. 5.

That is to say, bulkhead plates 19 and 20 having any crosssectionalshapes are connected with each other at a rotating joint through a pin21. The lower bulkhead plate 19 is connected so as to be rotatablearound a fixed pin 18 and the upper bulkhead plate 20 is movable whilesliding between guide 1 and a guide roller 22.

A seat plate 23 is fixed to the bulkhead plate 20 or 19 so that theforce finally pushing and pulling the bulkhead plate can be given to theseat plate 23. The positions of the bulkhead plates 19 and 20 are sodetermined that a desired crosssectional area of the throat parts B andQ can be obtained.

The torque from the driving axle 17 is also transmitted as describedabove.

The variable cross-sectional area mechanism is constructed as follows:The first bulkhead plate has at one end a rotary axis fixed to the sideplate 7 and is connected at the other end in the form of a hinge withthe second bulkhead plate through a rotary axis rotatable around thesaid rotary axis fixed to the side plate 7, the second bulkhead plate isconnected at the other end with one end of the third bulkhead plate inthe form of a hinge as described above, a plurality of bulkhead platesare thus connected in turn and the forward end of the final bulkheadplate is of any cross-sectional form so as to move, while slidingbetween the guide and a guide roller. By means of this construction asabove mentioned the cross-sectional area can be made variable.

Further, when the rotating angle of the driving axis 17 and the torquetransmitting elements 12 and 16 of FIGS. 3 and 4 and 23 and 27 andbulkhead plates 19 and 20 of FIG. 5 are properly selected, the relationbetween the control variable and the gas flow rate can be made to be alinear function.

Dust collecting water pumped by means of another apparatus is sprayed byspray nozzles 8 through a header 9 and is injected into the parts B andQ. In the case of handling a large flow rate of gas, in order to injectthe spray into the entire throat part, a spraying assembly may beprovided, for example, inside the rotor. In the diffusing parts C and R,the raw gas and the spray droplets injected in the throat parts B and Qmix together and the dust in the raw gas is absorbed by the actions ofcontact, collision and diffusion. Then, in the turning part of the gasflow (not illustrated) provided after the gas scrubber, the waterdroplets containing dust are separated from the gas and the raw gas iscleaned. At the same time, the gas velocity gradually decreases and thedynamic pressure of the high velocity gas in the narrowest part iseffectively recovered as a static pressure. For the change of the gasflow rate to be treated, the clearances in the narrowest parts in thethroat pans B and Q of the present gas scrubber are varied so that thegas passing cross-sectional area of the narrowest parts can correspondto the respective gas flow rates. Further, by making the gas velocity inthe narrowest part constant, the pressure loss and dust collectingefficiency can be kept constant.

A further important advantage attributable to the construction of theequipment of the present invention will be made clear from thecomparison of FIG. 6 showing a graph of a variable cross-sectional areamechanism, which is provided with the guide plates 1 and 6, with FIG. 7showing also a graph of the variable cross-sectional area mechanism, inwhich however, the guide plates are removed. when comparing both FIGS. 6and 7 in view of FIGS. 8 and 9 showing graphs, in which the velocity andstatic pressure are taken on the respective ordinates and the distancefrom the inlet of the venturi scrubber is taken on the abscissa, it isfound that, when producing the same the gas velocity V in the throatpart 1 which constitutes one of the most important factors indetermining the dust collecting efficiency, for both cases of FIGS. 6and 7, the following differences are seen between them:

I. In the case of FIG. 7, between 1 and as the gas velocity suddenlychanges from V to V and the gas flow collides directly with the rotor 3,the loss of the static pressure at 1 will be considered to be P P I 2.Though the gas velocity is the same V =V 1 the static pressure useduntil then will be P P Therefore, until 1 the difference P P3 of thestatic'pressure loss will be already produced between the cases of FI68. 6 and 7.

3. The lowest static pressure will be reached atI Here, too, due to theinfluence from 1 to I in the upstream part, that is, due to the abovementioned points 1. and 2., there will be a difference P P between thestatic pressures of both and P P 4. In the case of FIG. 7, between I andthe vortexes and separation of boundary layer are produced on thedownstream side of the rotor and the static pressure P, including thestatic pressure portion used already as a dynamic pressure will be lostand only P P will be recovered as a static pressure.

5. On the other hand, in the case of FIG. 6, the vortexes and separationof boundary layer are only slightly produced on the downstream side and,as the guide plate 6 is provided to gradually reduce the velocity from Vto V between 1 and I there will be only a slight loss and the staticpressure I, including the static pressure portion already used as adynamic pressure will be effectively recovered to P 6. That is to say,in comparing the static pressure recovered portion P,,P in FIG. 6 andthe static pressure recovered portion P P in FIG. 7 between I, and 1with each other, it will be found that, as P -,P P P and P P thepressure loss between [0d 16 will be P P As is evident from the abovementioned points I. to 6., an

advantage of the equipment of the present invention in power costs andequipment costs, which correspond just to the difference P P of thepressure loss, is obtained in the case of FIG. 6.

An example of the application of the gas scrubber of the presentinvention to a small-sized apparatus for recovering waste gas from aconverter in an unburnt state shall be explained in the following:

For treating an exhaust gas, which fluctuated in amount to be treatedfrom 0 to 1700 Nm3/l-I and had a temperature of 40 C., the internalpressure of the gas cooler was maintained at a certain value, whileadjusting the amount to be sucked-in by means of the equipment of thepresent invention.

The adjustment of the internal pressure of the gas cooler was favorable.The results of the measurements of the respective amounts were asfollows:

Test N 0. 1 2 3 Maximum exhaust gas volume in Nm /H 1, 500 1, 425 1, 250Mean pressure loss in mm. of Water column 3 963 1, 175 Pressure loss inmm. of water column when the exhaust gas flow rate was maximum 720 7801, 050 Amount of injected water in liters/Nrn tor the maximum exhaustgas flow rate 7 1. 4 2. 4 Dust collecting efiiciency in percent 98. 499. 2 99. 2 Amount of blown oxygen in Nm /H 42s 136 431 Thus favorableresults were shown. 7

After the equipment was used without sweeping the respective parts formore than 8 months, the contamination degree of the respective partswith deposited dust was so slight as to have no influence on thefunctions of the respective parts of the present invention.

I claim:

1. A wet venturi type gas scrubber comprising a venturi tube having athroat part with a substantially rectangular cross-sectional areatransversely of the axis of said venturi tube, a mechanism in saidthroat part dividing the gas flow path in the throat part into twoparts, said mechanism being movable for changing the cross-sectionalareas of the parts of the gas flow path, an upstream gas flow guide fordividing the gas flow path into two parts and positioned in said venturitube on the upstream side of the throat part and the downstream end ofsaid upstream flow guide covering the greater part of said movablemechanism, a downstream gas flow guide positioned in said venturi tubeon the downstream side of said throat part for preventing vortexes frombeing produced in the gas flow, said downstream gas flow guide havingthe upstream end in con tact with said movable mechanism, and meansconnected to said throat part for injecting a liquid into the throatpart.

2. A gas scrubber as claimed in claim 1 in which said gas flow guidesare wedge-shaped with the broad ends at said movable mechanism.

3. A gas scrubber as claimed in claim 1 in which said movable mechanismcomprising a rotor shaft extending transversely of the throat part, anda rotor mounted on said shaft, said rotor having a rectangularlongitudinal cross section and having a transverse cross section whichhas a different length than width.

4. A gas scrubber as claimed in claim 3 in which said rotor has atransverse cross section bounded by a closed curve.

5. A gas scrubber as claimed in claim 1 in which said movable mechanismcomprises a pair of spaced flexible and stretchable plate membersextending along the inside portions of the throat parts, and platemoving means between said plate members and coupled to said platemembers for bending the plate members outwardly into the throat parts.

6. A gas scrubber as claimed in claim 1 in which said movable mechanismcomprises two spaced sets of bulkhead plates extending along the insideportions of the throat parts, each set including a first bulkhead platehaving one end pivotally mounted on the venturi tube adjacent one gasflow guide, and

a second bulkhead plate slidably mounted adjacent the other gas flowguide and hingedly coupled to said first bulkhead 5 plate, and platemoving means between said sets of plates and coupled to said sets ofplates for moving the sets of bulkhead plates outwardly into the throatparts.

1. A wet venturi type gas scrubber comprising a venturi tube having athroat part with a substantially rectangular crosssectional areatransversely of the axis of said venturi tube, a mechanism in saidthroat part dividing the gas flow path in the throat part into twoparts, said mechanism being movable for changing the cross-sectionalareas of the parts of the gas flow path, an upstream gas flow guide fordividing the gas flow path into two parts and positioned in said venturitube on the upstream side of the throat part and the downstream end ofsaid upstream flow guide covering the greater part of said movablemechanism, a downstream gas flow guide positioned in said venturi tubeon the downstream side of said throat part for preventing vortexes frombeing produced in the gas flow, said downstream gas flow guide havingthe upstream end in contact with said movable mechanism, and meansconnected to said throat part for injecting a liquid into the throatpart.
 2. A gas scrubber as claimed in claim 1 in which said gas flowguides are wedge-shaped with the broad ends at said movable mechanism.3. A gas scrubber as claimed in claim 1 in which said movable mechanismcomprising a rotor shaft extending transversely of the throat part, anda rotor mounted on said shaft, said rotor having a rectangularlongitudinal cross section and having a transverse cross section whichhas a different length than width.
 4. A gas scrubber as claimed in claim3 in which said rotor has a transverse cross section bounded by a closedcurve.
 5. A gas scrubber as claimed in claim 1 in which said movablemechanism comprises a pair of spaced flexible and stretchable platemembers extending along the inside portions of the throat parts, andplate moving means between said plate members and coupled to said platemembers for bending the plate members outwardly into the throat parts.6. A gas scrubber as claimed in claim 1 in which said movable mechanismcomprises two spaced sets of bulkhead plates extending along the insideportions of the throat parts, each set including a first bulkhead platehaving one end pivotally mounted on the venturi tube adjacent one gasflow guide, and a second bulkhead plate slidably mounted adjacent theother gas flow guide and hingedly coupled to said first bulkhead plate,and plate moving means between said sets of plates and coupled to saidsets of plates for moving the sets of bulkhead plates outwardly into thethroat parts.